Mineral of thulium also containing aluminium and copper (6)
I believe the answer is:
talcum
'mineral' is the definition.
(I know that talcum is a type of mineral)
'thulium also containing aluminium and copper' is the wordplay.
I cannot really see how this works, but
'aluminium' could be 'al' (Al is the chemical symbol for aluminium) and 'al' is found within the answer.
'copper' could be 'cu' (chemical symbol) and 'cu' is found in the answer.
'thulium' could be 'tm' (Tm is the chemical symbol for thulium) and 'tm' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for talcum that I've seen before include "Kind of powder" , "Soft powder" , "Bathroom mineral" , "Type of powder" , "Perfumed powder" .)